Nonfogging coating compositions



Patented Mar. 6, 1945 NONFOGGING COATING COMPOSITIONS Richard Charles Wood, Philadelphia, and Harry Ross Young, Aldan, Pa., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application December 17, 1941, Serial No. 423,314

.6 Claims.

This invention relates to coating compositions and more particularly to pigmented coating compositions. It relates further and still more particularly to coating compositions used for interior decorative and protective purposes in buildings in which photographic emulsions are used or prepared.

In the manufacture of photographic materials, such as positive or negative films and plates, paper and even the photographic emulsion, every possible precaution must be taken to avoid the presence of contaminating materials which might affect the very sensitive photographic emulsion and thus produce an unsatisfactory or non-usable product. This often entails the absolute elimination of even minute traces of contaminating materials since large quantities of expensive materials may be spoiled even by the presence of traces of such contaminating substances. The interior of the buildings or rooms in which such products as noted above are manufactured must be kept scrupulously clean which requires frequent washing of the entire interior of the building or room. In some instances this washing is carried out daily by means of a high pressure stream of hot water. It is obviou that such treatment requires that the Walls, ceilings and floors of such buildings or rooms be protected with suitable coatings in addition to the desirability of imparting a suitable decorative effect.

The most or one of the most common difficul-- ties resulting from contaminating materials is known as fogging which manifests itself in a manner similar to that which would result from exposure of the materials to actinic rays. It is, of course, imperative to avoid contamination which might produce such damage if successful manufacture of such photographic products is to be carried on. It has been found that one source of such contamination may be the protective and decorative coating used on the Walls, ceilings and floors of the buildings or rooms in which the manufacturing operations are carried out. At the present time various types of coating compositions or paints are used but with only partial success. Chlorinated rubber paints do not cause fogging of the photographic emuls on but cannot be successfully used since they cause other difficulties. Phenol-formaldehyde resin-China-wood oil vehicle paints cause fogging when freshly applied, and for some definite period thereafter, as from several days to one week, and then apparently lose this objectionable property but they possess poor color retention and are expensive particularly in view of the very limited supply of China-wood oil. The so-called dammar gum paints are satisfactory from the standpoint of being substantially free from causing fogging but their service life is short, the coatings becoming brittle and in a relatively short time, crack and peel. This introduces another source of contamination which is objectionable, namely, that these coatings do not withstand the washing treatment as previously described. The so-called orthodox oleoresinous or straight oil paints are entirely unsatisfactory in that they cause severe fogging. The fatty oil or fatty oil acid modified polyhydric alcohol-polycarboxylic acid resin vehicle paints or enamels are excellent from the standpoint of durability, resistance to repeated washings and general service life but they cause fogging initially and this fogging may increase in intensity for a few days after application. If such materials were free from the contaminating effect of fogging, their use would be the most desirable from every standpoint and would solve a troublesome problem in the manufacture of photographic material. This also applies to the dryin oil-resin varnish vehicle base coating compositions.

This invention therefore presents as the principal object the provision of means for producing decorative and protective coating compositions which when applied to the walls, ceilings and floors of buildings and rooms in which photographic emulsion are prepared or used, will be substantially free of contaminating such photographic emulsions by causin fogging.

Another object is the provision of decorative and protective coating compositions for use where photographic emulsions are prepared or used and free from causing fogging, in which the film-forming vehicle is substantially a fatty oil or fatty .oil acid modified polyhydric alcoholpolycarboxylic acid resin or a drying oil-resinvarnish.

Still another object is the provision of such coating compositions which are substantially free from causing-fogging of photographic emulsions and from other objectionable contaminants and tective coating composition. Urea is not the equivalent of thiourea in this invention. p

The invention will be more fully understood by the following examples which are given by way of illustration but not by way of limitation. The parts are by weight.

Exams: I

Mill white paint or enamel larts Calcium base titanium dioxide pigment 6.5 Titanium dioxide pigment 23.! Zinc oxide 3.6 Alkyd resin A 20.4 Drier solution 0.5 Aromatic hydrocarbon solvent 41.4 Thiourea 3.9

Alkyd resin A is an approximately 34/14 per cent linseed oil/China-wood oil modified glyceryl phthalate.

The drier solution is a solution of cobalt naphthenate in mineral spirits containing the equivalent of 2 per cent metallic cobalt.

This composition may be conveniently prepared by dispersing the pigment in a portion of alkyd resin in solution in a pebble mill or other convenient means and then adding under thorough agitation the remainder of the alkyd resin, drier and hydrocarbon solvent. Other convenient or readily available means well known to those skilled in the art may be used in preparing the composition. The thiourea may be conveniently introduced with the pigments in the dispersion operation.

This composition, when used as a protective and decorative coating on the walls, etc. of buildings or rooms where photographic emulsions are being made or used in the manufacture of other photographic materials, produces no fogging, either initially or during the service life of the coating. The coating produced by the composition is further highly resistant to the repeated washings to which it is subject and fulfills every requirement exacted from material required for this purpose. The same composition containing no thiourea, while yielding a satisfactory service life, is unsatisfactory for use in that it causes severe fogging of photographic emulsions or products being made therefrom.

EXAMPLE 11 Mill white paint or enamel Parts Calcium base titanium dioxide pigment--- 6.7 Titanium dioxide pigment; 26.2 Zinc oxide 3.6 Aliwd resin A 20.5 Drier solution 0.4- Aromatic hydrocarbon solvent 41.3 Thiourea 1.3

The alkyd resin and drier solution used in this composition were as described under Example I. Other driers may be used in this composition as well as in the examples of other compositions in which it is desirable to use driers and such use will be readily apparent to those skilled in the art of preparing such compositions.

The composition may be prepared as described under Example I and the use of the finished enamel or paint produces no fogging of photographic emulsions or products made or being made therefrom. A similar composition but containing no thiourea is, however, unsatisfactory from the standpoint of producing no fogging even though its ordinary service life is satisfactory.

Exams: 111

Mill white paint or enamel Parts Calcium base titanium dioxide pigment--- 6.7 Titanium dioxide pigment 26.7 Zinc oxide 3.8 Diphenyl thiourea (symmetrical) 1.1 Alkyd resin A 20.5 Drier so 0.4 Aromatic hydrocarbon solvent 40.8

The ingredients used in this composition and the preparation thereof are as previously described. Coatings of this composition are free from producing any fogging eflects, retain their whiteness moderately well, and give long and satisfactory service. The absence of any fogging effects manifests itself in th compositions of the present invention not only initially but throughout the entire service life of the coatings which may vary between one and five years.

A similar composition as to ingredients and substantially as to quantity of ingredients, but containing 2.2 per cent of diphenyl thiourea, yields the same desirable and satisfactory results when used as a decorative and protective coating composition as the previously described products.

nish 52.4 Creosole solution 2.0 Mineral spirits 7.0

The drying oil-phenol-formaldehyde resin varnish is a 50 gallon perilla oil (19%) -China-wood oil (56%) linseed oil (25%) amberol-varnish containing 60% solids.

The creosole solution used is a 10% solution of creosole in mineral spirits. This material serves as an anti-skinning agent and may be replaced by equivalent materials serving the same purpose. If desired. a fiocculating agent, such as soya bean lecithin (50% solution in mineral spirits) to the extent of 0.1 part, may be used in the composition replacing an equivalent amount of mineral spirits. If desired. other flocculating agents may be used. Such modifications are well known to those skilled in the art and constitute in themselves no part of the present invention.

This enamel may be prepared by dispersing the pigments and the thiourea'in a portion of the drying oil-phenol-formaldehyde resin varnish in a ball mill or other suitable type of pigment dispersing equipment and then adding under thorough agitation the remaining ingredients.

This composition is completely tog-resistant whereas the same composition containing no thiourea will exhibit severe fogging.

Drying oil-resin varnish A is a 25 gallon Chinawood oil-phenol-formaldehyde varnish containing 60% solids.

Drying oil-resin varnish B is a 50 gallon Chinawood-linseed oil-rosin varnish containing 45% solids.

The hydrocarbon solvent is a mixture of liquid aliphatic and aromatic hydrocarbons in the approximate proportion of 36 per cent aliphatic and 64 per cent aromatic hydrocarbons.

The composition may be conveniently prepared by dispersing the pigments (other than the Ferrite yellow) and the thiourea in a portion of the drying oil-resin varnish A in a pebble mill or other suitable type of pigment dispersing equipment, and then adding under thorough agitation the remainder of the ingredients. The Ferrite yellow pigment is separately dispersed in drying oil-resin varnish B and added as a tinting paste.

This enamel is particularly applicable to machinery or other equipment or to interior or exterior surfaces where exposure to acids or other chemicals is encountered.

In place of the fatty oil modified alkyd resins shown in the examples other drying or semi-drying fatty oil or oil acid modified alkyd resins may be used. Such alkyd resins are well known in the art of preparing paints and enamels and the particular choice will be governed largely by particular characteristics desired in the finished product. Various other drying oil-resin (natural or synthetic) varnishes may be used in addition to those given in the examples and their choice will also be governed to a large extent by the characteristics desired in the finished product. While the fog inhibitors or anti-fogging agents are effective when used in so-called straight oil paints. their use with such film-forming vehicles is not preferred due to the great increase i drying time I imparted to the compositions.

The use of such compositions for practical purposes is thus not preferred and in addition the service life of such compositions is not the most satisfactory.

The compositions of the present invention are not limited to the use of any particular pigment or combination of pigments since various colored isiactory non-fogging properties.

While the examples show the use 01' from 1.1 per cent to 3.9 per cent of the anti-fogging agents or tog inhibitors, thiourea, and diphenyl thiourea based on the total composition, an amount less than 0.4 per cent begins to be ineffective whereas more than 4.0 per cent while effective is not economical and therefore the-preferred range for all practical purposes is between 0.4 per cent and 4.0 per cent.

The products oi. the present invention are generally applicable as decorative and protective coating compositions for various surfaces, such as wood, metal, plaster, etc. They are more particularly adaptable for producing decorative and protective coatings for the interior of buildings or rooms in which photographic emulsions are prepared or used in preparing other photographic materials in that they are not a source 01. contamination in producing fogging oi the photographic emulsions or other materials made therefrom. In addition they fulfill all the service requirements of coating compositions used for such purposes. They may be applied by conventional methods as brushing or spraying and require no special precautions in their application.

It will be apparent from the above that an advance has been made in the art of decorative and protective coating compositions in that such compositions have been provided which satisfy the requirements of being non-fogging to photographic emulsions or products made therefrom and yielding a long service life under drastic conditions of cleaning, etc. The anti-fogging property of the compositions is retained throughout the service life of the coatings. Further the antifogging (or non-fogging) compositions retain all the desirable or required properties such as gloss or dullness as the case may be, retention of color. ease of application, etc. as possessed by similar products from which the anti-fogging agent has been omitted. In addition the use of the compositions is economical both from the standpoint of eliminating loss through fogging of photographic emulsions and their long service life under drastic treatment. Other advantages will be readily apparent to those skilled in the art of using such decorative and protective coating compositions.

It is apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore. it, is not intended to be limited except as indicated in the appended claims.

We claim:

1. A coating composition comprising an alkyd resin modified with a vegetable oil having drying properties and from about .4 to 4% of an anti-fogging agent selected from the group consisting of uncombined thiourea and dipheny) thiourea, said coating composition being substantially free from any tendency to fog photographic emulsions when in proximity thereto.

2. The composition of claim 1 in which the anti-fogging agent is thiourea and is present in amount between about 1.1 and 4.0 per cent.

3. The composition of claim 1 in which the anti-fogging agent is symmetrical diphenyl thiourea and is resent in amount between about 1.1 and 4.0 per cent.

4. An enamel comprising a pigment, a drying oil modified alkyd resin and about 4 per cent of thiourea, said enamel characterized in that it is substantially free from any tendency to log photographic emulsions when in proximity thereto.

5. An enamel having approximately the following composition by weight:

- Parts Calcium base titanium dioxide pigment- 6.5 Titanium dioxide pigment 23.! Zinc oxide 3.6 Alkyd resin modified with a drying vegetable i ,L 20.4 Drier so 0.5 Aromatic hydrocarbon solvent "a---" 41.4 Thiourea 3.9

aamoaa 6. A coating composition comprising a resin modin'ed with a vegetable oil having drying properties and from about .4 to 4% of an anti-fogging agent selected from the group consisting of uncombined thiourea and diphenyl thiourea, said coating composition being substantially tree from any tendency to i'og photographic emulsions when in proximity thereto.

' RICHARD CHARLES WOOD.

HARRY ROSS YOUNG. 

